The present invention relates to a medical device for insertion into a physiological lumen. More specifically, the present invention relates to a balloon catheter for delivering a therapeutic substance to a blood vessel.
Increasingly, the diseases of the arteries are being treated with percutaneous interventions such as percutaneous transluminal angioplasty (PTA) instead of with vascular surgery. Percutaneous interventions are less invasive, cost efficient, and have lower risks. Typically during a PTA procedure, a catheter assembly having a balloon is introduced percutaneously into the cardiovascular system of a patient via the brachial or femoral artery. The catheter assembly is advanced through the vasculature until the balloon is positioned across an occlusive lesion. Once in position across the lesion, the balloon is inflated to a predetermined size to radially compress against the atherosclerotic plaque of the lesion to remodel the lumen. The balloon is then deflated to a smaller profile to allow the catheter to be withdrawn from the patient""s vasculature.
Although PTA has proven to be an extremely effective procedure, many patients develop restenosis over the several months following the procedure, which may require another angioplasty procedure or a surgical by-pass operation. Restenosis is thought to involve the body""s natural healing process. Angioplasty or other vascular,procedures injure the vessel walls, removing the vascular endothelium, disturbing the tunica intima, and causing the death of medial smooth muscle cells. Excessive neoinitimal tissue formation, characterized by smooth muscle cell migration and proliferation to the intima, follows the injury. Proliferation and migration of smooth muscle cells (SMC) from the media layer to the intima cause an excessive production of extra cellular matrices (ECM), which is believed to be one of the leading contributors to the development of restenosis. The extensive thickening of the tissues narrows the lumen of the blood vessel, constricting or blocking blood flow through the vessel.
To reduce the development of restenosis, therapeutic substances have been administered to the treatment site. For example, anticoagulant and antiplatelet agents are commonly used to inhibit the development of restenosis. In order to provide an efficacious concentration to the target site, systemic administration of such medication often produces adverse or toxic side effects for the patient. Local delivery is a preferred method of treatment in that smaller total levels of medication are administered in comparison to systemic dosages, but are concentrated at a specific site. Local delivery, thus, produces fewer side effects and achieves more effective results.
One technique for the local delivery of a therapeutic substance is through the use of porous balloons attached to a distal end of a catheter assembly. The expansion of the balloon, which in effect results in the dilation of the occluded region, is accomplished by injecting a therapeutic substance into the balloon. The use of a therapeutic substance as an expansion fluid additionally functions as a medicament for the diseased region, as the therapeutic substance is discharged from the porous balloon during and subsequent to the expansion therapy. Unfortunately, a shortcoming associated with this procedure is that the therapeutic substance is continuously carried off by the blood flow as it is being discharged into the vessel. The loss of the therapeutic substance from the treatment site results in an ineffective treatment of the target site and adverse exposure of the substance to healthy tissues.
Therefore, what is needed is a device that regulates blood flow in a treatment space in a physiological lumen, can deliver a therapeutic substance to the treatment space, and prolongs the residence time of the substance at the treatment space.
In accordance with one aspect of the invention a medical device for insertion in a physiological lumen is provided. The medical device includes a catheter assembly having a first balloon element and a second-balloon element. The second balloon element is capable of being moved towards and away from the first balloon element to create a treatment space when the first and second balloon elements are inflated. A first port can be in fluid communication with the treatment space for supplying to or withdrawing from the created treatment space a therapeutic substance.
In accordance with one embodiment of the invention a second port is in fluid communication with the treatment space, wherein the second port is used for supplying to or withdrawing from the created treatment space the therapeutic substance. Accordingly, the first port can be used to withdraw a substance that is supplied from the second port.
The catheter assembly can include a first catheter tube supporting the first balloon element and a second catheter tube telescopically disposed over the first catheter tube and supporting the second balloon element. The first port can be disposed on the first catheter tube and in fluid communication with a lumen of the first catheter tube. The second catheter tube can include a central lumen for telescopically receiving the first catheter tube, wherein the inner diameter of the central lumen is sufficiently larger than the outer diameter of the first catheter tube so as to allow for the injection and withdrawal of a therapeutic substance from the gap between the surfaces.
In accordance with another aspect of the invention, a method for delivering a therapeutic substance to a physiological lumen is provided. The method comprises inserting a catheter assembly into a physiological lumen; positioning a first balloon element disposed on the catheter assembly at a target area within the physiological lumen; positioning a second balloon element relative to the first balloon element; inflating the first and second balloon elements to create a treatment space; and releasing a therapeutic substance through a first port of the catheter assembly in the treatment space. In one embodiment, the method further comprising removing the therapeutic substance through a second port of the catheter assembly.